Pests and Diseases
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Item Agrobacterium-Mediated Transformation of Elite Kenyan Maize Germplasm with Cry3a Gene for The control of the Lager Grain Borer and Maize Weevil(Catherine O T, 2013) Catherine, O.T.In Kenya maize (Zea mays L.) is the most important staple food. Owing to its predominant role, food security in the future cannot be achieved without major increases in cereal production. An efficient in vitro regeneration and transformation system holds great potential for genetic improvement of maize against production constraints. This study was conducted with the objective of assessing the regenerative capacity, genetic transformation of Kenyan maize genotypes, and efficacy of transformed maize in controlling maize pests. Six Kenyan inbred lines and four CIMMYT lines and their single crosses were evaluated for their in vitro response on three different media (MS, N6, and N6CL). The embryogenic callus induction and regeneration capacity were higher on MS than on N6 basal salts. Plant regeneration was influenced by genotype. Transformation experiments were carried out using Agrobacterium tumefaciens strain EHA 1 0 1 containing pTFI02 binary vector harbouring a GUS gene. The transformation frequency was highest in 104 (15.2%) and lowest in QPM. The highest transformation efficiency was recorded in inbred T04, 104, and their crosse with CML 216 ranged from 2.4% to 3.0%. The transgene was detected in all the maize genotypes using GUS assays, and PCR. Maize genotypes were transformed using a Bacillus thuringiensis tenebrionis gene Cry3A . The highest transformation frequency was recorded in three inbred lines, H04, T04 and 104 (9.3%, 12.2% and 13.4% respectively). The transformation efficiency ranged between 0.5% to 2.5%. PCR and RT-PCR amplification of the Cry3A gene, and the DAS-Elisa confirmed the presence of the gene To, T 1 and T 2 generations. Insect bioassays established that transgenic maize provided protection against the larger grain borer and maize weevil This study established a reproducible regeneration and transformation system for tropical maize, which can be used in a pest management programme.Item Annotated Host List of Uganda Parasitic Fungi and Plant Diseases—Part III.(1937) Hansford, C.G.; Department of Agriculture, Uganda Protectorate.These two further instalments of the author's list of parasitic fungi and plant diseases so far recorded in Uganda are on the same lines as the first [R.A.M., xvi, p. 550], and include hosts belonging to 37 families. Armillaria mellea is stated to cause the most important disease of tea in Uganda [ibid., viii, p. 202]. Cotton wilt (Verticillium albo-atrum) [ibid., xv, p. 150; xvi, p. 455] is now known from most cotton areas south of Lakes Albert and Kioga and is increasing every year. The fungus is distributed all over Uganda in seed obtained from diseased plants, and under present conditions dissemination by this means cannot be prevented. It is probable that V. albo-atrum is locally the chief cause of cotton wilt. The fungus was recently discovered attacking cassava at Bukalasa. Mycosphaerella areola, the ascigerous stage of Cercosporella gossypii (syn. Ramularia areola] [ibid., xiv, p. 629] was recorded in its ascigerous stage on cotton. Gibberella fujikuroi, a common saprophyte on dead cotton plants, causes a disease of cotton seedlings simulating sore shin. Cladosporium album [Erostrotheca multiformis: ibid., xvi, p. 322] is recorded on beans (Phaseolus) (on which it causes little damage) and peas.Item Assessment and Management of Potato Bacterial Wilt (Rastonia Solanacearum) In the North Rift Valley Region of Kenya(Thomas K K, 2008) Kwambai, T.K.Bacterial wilt (Ralstonia solanacearum) is a serious disease in potato production areas in Kenya, including the North Rift Valley region. The soils in these areas are acidic, which may favour the disease and not as such the crop. Studies were carried out to assess the status of potato bacterial wilt and to determine the effect of soil liming on its management. A survey was conducted in Trans Nzoia, Uasin Gishu, Keiyo and Marakwet districts of the North Rift region of Kenya during the short rainy season, October-December 2006. A questionnaire was administered to 256 potato growers, soil samples taken and field observations made. in each district two major potato growing divisions were assessed. The study areas and potato fields were randomly but purposefully selected on the basis of potato cropping intensity, current potato field size and crop growth stage.Item Assessment of Pesticide Multiplicity in Potato Production and Storage in Bomet, Kenya(East African Agricultural and Forestry Journal, 2022-06-02) Oyoo, J.I.; Abong, G.O.; Okoth, M.W.; Nyongesa, M.W.; Kenya Agricultural and Livestock Research Organization ; University of NairobiPotato (Solanum tuberosum L.) crisps are among the most appealing potato products to middle and high income households including women, youth and children and are produced from potatoes mainly grown in Bomet County. A cross-sectional survey was done in 305 potato growing households in Bomet County to establish categories of pesticides used in potato production and storage, level of awareness of pesticide residues and perceptions of risks associated with pesticide contamination at ingestion of potato and its products. Questionnaires were administered through simple random sampling of potato farmers, disaggregated according to their gender, level of education and age. The parameters of interest were type of pesticides applied, knowledge of banned or restricted pesticides and knowledge of presence of pesticide residues in potatoes and risks involved. Data was collected using open data kit (ODK) and analysis done using Statistical Package for Social Science (SPSS) software version 21. Descriptive statistics were used to generate socio-demographic characteristics (gender, age, education levels) and analysis of variance (ANOVA) was performed on the data about knowledge of pesticides. Results are presented as percentages, means and frequency distribution. Differences between the means were calculated at 95% level of significance using Fischer’s test. The study showed that 72% of the respondents were male and 28% female. Most of the potato farmers aged between 20- 59 years (87.2%). A majority of the sampled farmers (26.9%) had up to tertiary level education while 31% attended primary school only. About 95% of the respondents used fungicides to control late blight while 14% used insecticides for pest control. It is worth noting that only 0.6% of the respondents used dimethoate and Diazinon, restricted/banned chemical compounds in Kenya. A significant number of fungicides (47%) used were classification class II which are moderately hazardous. Most respondents (79%) could not tell which pesticides had high residues. However, majority (84%) perceived that potatoes in the markets or those cooked at home, restaurants or hotels contained pesticide residues which could harm consumers. The study demonstrated the need for more awareness creation on appropriate pesticide use and sensitization on pesticide residues in potato production.Item Centre for Overseas Pest Research(I C I P E, 1961-1962) Johnstone, D.R.; Overseas Development AdministrationIn keeping with the general policy of streamlining Government Departments and in order to strengthen and improve certain aspects of British aid to agricultural research and development overseas it has been decided that certain scientific units of the Overseas Development administration, which are primarily engaged in the entomological fields, should be merged into a single organisation. The units involved are the Anti-Locust Hese8lch Centre, the Tropical Pesticides Research Unit, the Tropical Pesticide, Research Head quarters and Information Unit and the Termite Research Unit.Item Characterization and Pathogenicity of Symbiotic Bacteria Associated with Entomopathogenic Nematode: Steinernema Species KALRO(East African Journal of Science, Technology and Innovation, 2021-09-25) Ngugi, C.N.; Wachira, P.M.; Mbaka, J.N.; Okoth, S.; Mangua, P.W.; Kenya Agricultural and Livestock Research Organization (KALRO) ; University of NairobiThe soil inhibiting entomopathogenic nematodes (EPNs), in the family Steinernematidae and Heterorhabditidae, are useful insect biological control agents. They have been used in the management of economically important crop pests. The EPNs are mutually associated with symbiotic bacteria genus Xenorhabdus and Photoharbdus respectively. The study aimed to isolate, characterize and evaluate the pathogenicity of symbiotic bacteria associated with EPN Steinernema sp. Kalro (Accession MW151701). The EPN Steinernema sp. Karlo was multiplied using the insect baiting technique. Its bacteria symbiont was isolated and characterized based on microscopic, biochemical, and physiological features like Gram staining, urease, motility test, and glucose fermentation test). Molecular identification and phylogenetic analysis were performed on 16S rDNA nucleotide sequence. Pathogenicity of the bacteria isolate was evaluated against Tuta absoluta larvae with mortality data recorded after 24 and 48hours of exposure to the bacterial cell suspension. The bacteria were found to be motile and glucose fermentation positive. Sequence analysis of 16S rDNA region resulted in 1500bp sequence with maximum similarity of between 97 and 98.93%, with Xenorhabdus spp Accessions from Genbank. It closely matched to Xenorhabdus sp. My8NJ with 98.93% similarity (Accession AB507811.1). Mean percent larval mortality of 68±4.9 and 88±8.0 in the lowest cell suspension was observed in 24 and 48h of exposure. It’s concluded that, the symbiotic bacteria associated with Steinernema sp. Kalro is Xenorhabdus sp. strain Kalro Genbank Accession MW245845. The bacteria is a potential biological control agent against Tuta absoluta larvae. Further classification of the bacteria to species level and pathogenicity trials in the screen house and field are recommended.Item Characterization and Pathogenicity Test of Entomopathogenic Nematode Steinernema Species-Kalro(Canadian Center of Science and Education, 2021-02-15) Ngugi, C.N.; Wachira, P.M.; Mbaka, J.N.; Okoth, S.; Haukeland, S.; Mburu, H.M.; Adhiambo, M.; Sirengo, D.K.; Kenya Agricultural and Livestock Research Organisation ; University of Nairobi ; International Center of Insect Physiology and EcologyEntomopathogenic nematodes (EPNs) are worldwide soil-dwelling insect parasitic nematodes. They are potential pest bio-control agents a key component of Integrated Pest Management (IPM) programs. This study aimed to characterize and evaluate the pathogenicity of an EPN isolate from Kenya. The nematode was isolated from soils using insect bait technique and both morphological and molecular identification was performed. Efficacy of the isolate was evaluated against Tomato leafminer larvae (Tuta absoluta Meyrick.) using dose-based treatments of 0-control, 100, 150, 200, and 250 infective juveniles (IJs/ml). Morphological analysis revealed body length (L) of 835(659-987) µm and 1781 (1297-2097) µm from fresh IJs and males respectively. Males lacked a mucron. The isolate was characterized by the partial sequence length of 877 bp of the ITS region. Blastn results indicated the EPN isolate had a similarity match of 81-92% with Afro-tropical Steinernema species. It matched with Steinernema sp. (AY230186.1) from Kenya at 92% and Sri Lanka (AY230184.1). Phylogenetic analysis placed the isolate together with Steinernema sp. (AY230186.1) and (AY230184.1) with a bootstrap value of 100%. Maximum mean larval mortality (80%; 96%) was achieved 24 and 48 h post-treatment at concentration 150 IJs/ml. All nematode concentrations achieved over 50% mean mortality after 24 h period. There was a significant difference (P = 0.001) between doses 150 and 200 IJs/ml. From the study, it was concluded that the nematode isolate was Steinernema sp now referred to as Steinernema sp. Kalro (Genebank Accession MW151701). The EPN has the potential for development as a biological control agent against T. absoluta.Item Charops Sp. (Hymenoptera: Ichneumonidae) A larval parasite of Orgyia Mixta Snell(1970) Migunda, J.; East African Agricultural and Forestry Research Organization, Muguga, KenyaCharops sp. is probably an important parasite 10 the natural control of O. mixta. The parasite attacks O. mixta during the early larval stages from the last instar larvae. The larval, cocoon, and adult stages of the parasite are described.Item A Contribution to the Biology of the Musophagiformes, the So-Called Plantain-Eaters.(1938) Moreau, R.E.; AMANI(1) The various names indicating plantain (banana) eating, by which these birds have been called, have no foundation whatever in their habits in nature. As the English name, " Turacos " is preferred for the Order as a whole. (2) The growth and habits of T. fischeri and T. persa are described from the age of about one month onwards. Young specimens of Crinifer and Corythmola are described. (3) It is a character of the Order that the young are completely clothed with (neossoptile) down; it is probable, but not proved, that they are all born with it. At the age of about four or five weeks this has been replaced as bodycovering by a dense growth of down-feathers (semi-plumes), but on the head and neck it is more or less completely shed (at the age of about two months) before any other covering is ready to take its place. The ear is, however, specially protected at this stage. The coloured contour feathers only begin to appear about the tenth week. The pre-adult wing and tail are complete about the ninth and twelfth week respectively. Evidence (from captive birds) on the date adult plumage is assumed is hopelessly divergent.Item Control of insects attacking maize on the cob in crib stores(1958) Kockum, S.; Department of Maize and Produce Control, KenyaThe climatic conditions in Kenya normally prevent maize from drying out sufficiently in the field to allow immediate shelling. At harvest time the husk is removed and the maize on the cobs is stored in cribs until dry enough for shelling and delivery. For this and various other reasons the harvested crop is often kept in this manner for six to eight months or even longer. During this storage time on the farm before any control methods were introduced, ideal conditions existed for many pests to increase to large numbers causing considerable losses in weight and quality. In 1952 the Agricultural Department of Kenya made an investigation (unpublished) of losses in crib storage. Six untreated farm cribs in different districts were shelled out after four months, and six further untreated cribs were shelled out after six months. After correction for changes in moisture content the average weight loss during storage was found to be 9.6 per cent after four months and 23.1 percent after six months. Calandra oryzae L. and sitotroga cerealella Olivo attack the growing crop, but build up mainly in the stores. From the cribs and stores these pests may spread to adjoining maize fields and to other grain crops such as wheat, barley and sorghum. The importance of reducing these enormous losses and preventing the pests from contaminating the growing crops has long been realizedItem The control of sorghum pests with insecticides in Eastern Uganda(1970) Davies J.C.; Jowett, D.; Serere Research StationTrials carried out over three seasons at Serere Research Stations, Uganda using insecticides for control of sorghum pests, particularly Atherigona varia Rond. (Diptera, Muscidae), are described. Insecticides used included endosulfan, phosphamidon, menazon, DDT and trichlorphon. the most successful control of sorghum shoot fly was obtained with endosulfan, particularly when it was applied six or more times.Item Control whiteflies in Citrus(Kenya Agricultural Research Institute, 2010) Kenya Agricultural Research Institute; Kenya Agricultural Research Institute Njoro.What is whitefly? • The whitefly is a serious insect pest of citrus in Kenya. • It causes serious damage when it attacks and sucks tender leaves of plants. • Heavy attack by whitefly can result in - weak trees with few leaves. - small fruits with little juice. - low fruit yields. - sooty mould in fruits that reduce the price of fruits even further.Item Detection of the Spotted Wing Drosophila, Drosophila suzukii, in Continental Sub-Saharan Africa(Springer, 2021-01-23) Kwadha, C.A.; Okwaro, L.A.; Kleman, I.; Rehermann, G.; Revadi, S.; Ndlela, S.; Khamis, F.M.; Nderitu, P.W.; Kasina, M.; George, M.K.; Kithusi, G.G.; Mohamed, S.A.; Lattorff, H.M.G.; Becher, P.G.; Swedish University of Agricultural Sciences ; International Centre of Insect Physiology and Ecology ; Kenya Agricultural and Livestock Research Organisation ; KEPHIS Headquarters ; Horticultural Crops Directorate (HCD)The spotted wing drosophila, Drosophila suzukii Matsumura, is an insect pest of soft-skinned fruit, native to Eastern Asia. Since 2008, a world-wide dispersal of D. suzukii is seen, characterized by the establishment of the pest in many Asian, American and European countries. While the potential for invasion of continental Africa by D. suzukii has been predicted, its presence has only been shown for Morocco in Northern Africa. Knowledge about a possible establishment in other parts of the continent is needed as a basis for pest management. In 2019, we carried out a first survey in three counties in Kenya to monitor for the presence of D. suzukii using traps baited with a blend of apple cider vinegar and red wine. A total of 389 D. suzukii flies were captured in a fruit farm at Nakuru county, with more female flies being trapped than males. We confirmed the morphological identification of D. suzukii using DNA barcoding. In 2020, we performed a follow-up survey at 14 locations in six counties to delimit the distribution of D. suzukii in the main berry growing zones in Kenya. The survey indicated that so far D. suzukii is restricted to Nakuru county where it was initially detected. This is the first study to provide empirical evidence of D. suzukii in continental sub-Saharan Africa, confirming that the pest is expanding its geographic range intercontinentally. Given the high dispersal potential of D. suzukii, a concerted effort to develop management strategies is a necessity for containment of the pest.Item Diversity of Banana Streak Virus In Kenya(Laura Shally Karanja, 2009) Karanja, L.S.Banana streak virus (BSV) is a serious constraint to the production of banana and plantain (Musa spp.) In Sub-Saharan Africa. BSV has been found to be present in virtually all the commercial banana cultivars in Kenya. Various studies have reported that the banana streak virus is caused by a range of BSV isolates. The ability to quickly and reliably detect BSV is a prerequisite to the management of the virus. A variability study of BSV in Kenya was carried out to develop suitable diagnostic techniques. Transmission of the disease is through several species of mealy-bug (Planococcus spp) but a more significant transmission is through infected vegetative propagation materials. In some Musa hybrids and derived cultivars, integration of BSV into the plant genome can cause subsequent infection when triggered by stress factors such as drought, tissue culture, temperature, and genomic hybridization. /11 Filro propagation has been identified as one of the main activation triggers of integrated sequences to cause systemic (episoma l) banana streak disease (BSD). This was especially observed in the B genome containing AAAB hybrids (FHIA 18 and FHIA 0 I/Go ld finger). The heterogeneous nature of the virus in the field hinders reliable detection by serological techniques. Integrated BSV sequences cause problems in direct molecular detection of virus particles by polymerase chain reaction (PCR). Hence, deoxyribonucleic acid (DNA) -based techniques, following serological trapping of the virus, immune-capture polymerase chain reaction (IC-PCR) has been found most reliable in the detection of BSV. The main objective of this study is to identify BSV isolates in Kenyan banana cultivars. Factors affecting the infection and expression of BSV was restudied to optimize the diagnostic protocol in order to help with virus indexing and consequently mass production of BSV-free banana seed li ngs. The work was accomplished through random collection of liclc1 banana material from various banana growing regions, serological analysis using Enzyme Iinked Immunosorbent Assay (ELISA) kit which confirmed 87% BSV infection. Isolation of nucleic acid from infected leaf samples, molecular characterization of BSV and sequence analysis of the clone enabled identification or about seven isolates. Three of the seven isolates were new isolates. Genome-based methods of detection such as nucleic acid hybridization and PCR amplification were used. Through screening of various antibodies and primers, their effectiveness in detecting BSV was determined. Tissue culture materials of 15 cultivars were evaluated for BSV re- infection and expression so as to determine the tolerant cultivars under field and greenhouse conditions and stage of infection and expression. Environmental factors such as nutrition that affect the expression of BSV were also studied. Statistical analysis system (SAS) for ANOVA and various bioinformatics packages were used for analysis of data for the experiments. Results indicated that BSV is associated with an increase of growth time, decrease of plant height, girth, number of leaves and high nitrogen leve ls. Cultivar, location and season also played a critical role in the expression of BSV. The study also confirmed that detection of new isolates was influenced by antibody type, concentration and antigen concentration. The available antibodies have limitations in the comprehensive detection of BSV. However, uses of genomic techniques were more effective than serological techniques. Based on amplification, cloning, sequencing, phylogenetic analyses, and pairwise comparison of the nucleotide sequence similarities of 80% and above (proposed criteria by the International Committee on Taxonomy of viruses (ICTV), three new isolates of BSV were identified and confirmed for the first time in Kenya. The isolates were Khabusi2 from Mt. Elgon region (EAH - AAA genome), Lisulya from Kisii region (EAH - AAA), and Nshule from Kisii region (EAH - AAA).Item The Ecology of Insect Parasites and Predators(1933) Varley, G.C.; Hope Department of Zoology (Entomology), Oxford UniversityThe Study Of parasitic and predatory insects has recently become more urgent because of difficulties in preventing serious crop damage and damage to stored products by insects of various kinds. With the discovery of modern insecticides it was expected by the optimists that problems of pest control were now soluble if not yet solved. Tests had shown the very high toxicity of these substances to insects, few of which could survive insecticide application in the field. The short-term effect was beneficial, with a satisfactory reduction of damage. Some pests, however, like the codling moth on apple trees, remained numerous enough to cause economic damage even when frequent insecticide sprays were used. Other pests, like the red spider mites, seemed in fact to be more serious where insecticide was used than without it.Item The Effect of Intercropping Maize and Cowpeas on Insect Pest Population(1989) Giga, D.P.; Munetsi, M.; University of ZimbabweHigher numbers of jassids (Empoasca spp.) and whiteflies were recorded m sole cropped cowpeas than in cowpeas intercropped with maize. There were no differences in numbers of pod sucking bugs (Nezara viridula, Anoplocnemis curvipes and Riptortus dentipes) and foliage beetles (Ootheca mutabilis) between sole cowpeas and cowpeas in two different intercroppmg systems. The numbers of these pests were, however, significantly lower in sole maize plots. Some of the reasons why insect pests are lower in intercropping systems are discussed.Item The Effect of Minimum Tillage and Herbicide Use on Bean Production(1991) Olango, V.O.; Michieka, R.W.; University of NairobiA two-year study on the research farm of the University of Nairobi, Kabete, suggested a need to identify adequate weed control methods for bean production under the minimum tillage system. Although alachlor and metolachlor at the highest rates tested effected some weed control, this was not as effective as in the hand-weeded treatments. Metribuzin, despite affording adequate weed control, was highly injurious to beans. At the rate of 0.7 kg ai/ha, metribuzin reduced the bean stand by over 50%. Yield of beans from conventional tillage treatments was superior to those from the minimum tillage system. Minimum tillage has some merit for bean production, but satisfactory weed control measures are needed.Item The Effects of Relative Humidity on the Development of Eggs and Nymphs of Acanthomia(1978) Egwatu, R.I.; University of IbadanStudies on the effects of relative humidity on the development of eggs and nymphs of A. tomentosicollis showed that relative humidifies in the range of 30 to 100 percent R.H. harl no significant effect on the rate of development of both the eggs and the nymphs. The percentage egg hatch which ranged from 90 to 100 percent was not affected by the relative humidity but, nymphs mortality was high at relative humidifies below 40 percent and above 90 percent R.H. Jhese results are discussed in relation to the environmental conditions which obtain in the ecological zone of the species.Item The Effects the Two Spotted Spider Mite, Tetranychus Urticae, of Dicofol Concentration and Deposit Distribution on the Leaf Surface(1968) Fisher, R. W.; Morgan, N. G.; Research Station, Canada Department of Agriculture, Department of Entomology, Long Ashton Research Station University of BristolDicofol was applied to bean leaf discs in various ways. The number of drops per disc, the concentration of dicofol in each drop, and the size of the drops were related to egg laying and mortality of adult female mites placed on the discs. Under the conditions of the experiment, an increase in concentration above normal field strength (0.046% active ingredient) had little effect, even though the deposits were discontinuous and similar to those expected from low volume spraying. Repellency of dicofol to mites was reaffirmed and toxicity effects were significant were about one-quarter of the leaf surface was covered by deposit.
